Hexafluoroacetone adduct

Af-Activation by BF3 to form complex 230 can be used to promote ortholithiation of pyridine itself , though not quinoline and isoquinoline (Scheme 112). Temporary formation of a pyridine-hexafluoroacetone adduct 231 achieves the same result. ... 

Huorothene vessel. Other methods include the decomposition of various nitrosyl adducts. In the present method, nitrogen dioxide is allowed to react at room temperature with an excess of potassium fluoride to produce nitrosyl fluoride, in nearly quantitative yields, as the only volatile product. The rate of formation of nitrosyl fluoride may be dramatically increased by first forming a potassium fluoride-hexafluoroacetone adduct which is subsequently thermally decomposed to yield potassium fluoride having a high surface area. 

Parameters reported for other fluoroaryl compounds in which the transition metal is not directly attached to the aromatic ring are given with structures [352] to [372], (115, 121, 201-203, 205-207) The structure of the hexafluoroacetone adduct [353], for which four signals in the aromatic region are reported, is not known. (115) The WFsO... 

Details have appeared of the preparation and variable-temperature F n.m.r. spectra of the phosphetan-hexafluoroacetone adducts (18). The trans-dimethylaminophosphorane (18 R = Me2N) on dissolving in hexa-fluoropropan-2-ol gave the hexafluoroisopropox3q)hosphorane [18 ... 

The variable-temperature n.m.r. of the diaryl phosphoramidite-hexafluoroacetone adducts (30) have been interpreted in terms of a substantial difference in apicophilicity between aryloxy- and amino-groups, changing substituents on nitrogen having little effect. The variable-temperature C, F, and n.m.r. spectra of the caged polycyclic phosphorane (31) have now been studied down to —165 °C. Permutational isomerization is still rapid at this temperature. 

Several papers have shown that trifluoroacetate derivatization is a useful method of characterizing alcohols, phenols, thiols, and primary and secondary amines, " while hexafluoroacetone adducts of phenols are also helpful. ... 

Me C C CHj4i CH2 CMe C( CHii) C(OH)(CF,)2],i (xv) cycloadditions of fluoroalkenes [(CFjlsCO + Ph P + CCl,Br--> (CFa)jC CCl y (xvi) determination of the relative apicophilicities of groups via n.m.r. studies on hexafluoroacetone adducts of phosphetans (see p. 251), (xvii) base-catalysed nucleophilic substitutions at five-co-ordinate phosphorus [reactions between (CFa)aCO and phosphonites, RCHj P(OMe)a, phosphinites, (RCH8)jP OMe, or tertiary phosphines, (RCHt)aP, where R = H or Me, provide a general source of 1,2-oxaphosphetans with five-co-ordinate phosphorus (see p. 251)], and (xviii) studies on bis(trifluoromethyl)thio-keten (see p. 251) (Scheme 36). ... 

There are two interesting featnres in the spectrum of the hexafluoroacetone adducts. First it illustrates clearly, the high resolution and information on structural aspects... 

Interestingly, the sulphenyl chloride FaNCClj SCI (see p. 99) yields (>70%) trifluoromethyliminosulphur difluoride when stored in contact with activated potassium fluoride [prepared by thermal decomposition of the potassium fluoride-hexafluoroacetone adduct (CF3)jCF-OK] at room temperature for 3 days. No mechanism has been proposed to account for the migration of the nitrogen. 

C. J. Schack, R. D. Wilson, and M. G. Warner, Chem. Comm., 1969, 1110. The increased reactivity of caesium fluoride treated in this manner is said to be comparable to that attained by decomposition of the caesium fluoride-hexafluoroacetone adduct. 

Addition of pyrazole to C—X double bonds is also common. Formaldehyde gives stable adducts (260) and (261) (69BSF2064), but in the addition to ketones, (262) is only observed at low temperatures (Section 4.04.1.3.3(i)). However, hexafluoroacetone forms a stable adduct (262 R = Cp3) that has been used as a chelating agent (Section 4.04.2.1.3(iv)). Addition of pyrazoles to aryl isocyanates affords (263) the addition is also reversible, but it requires high temperatures to dissociate the adduct (Section 4.04.1.5.1). 

Fluorodenitration of nitroaliphatics has been primarily restricted to polyni tromethanes (Table 9) Side reactions involving potassium nitnte by-product reduce yields of fluoromtromethane The novel use of the adduct of potassium fluoride with hexafluoroacetone in diglyme as a source of fluoride ion for the fluorodenitration of tetranitromethane significantly increases the yield of fluorotn nitromethane [102] (equation 29)... 

When hexafluoroacetone reacts with amides, urethanes [25], thioamides [26], amidines [27], sulfonamides [28, 29], sulfinainides [20], and f),0-dialkyl-amido-phosphates [27], the correspondmg semiamidals are formed m nearly quantitative yield The thermal stabihty of these adducts toward the retro reaction increases with the nucleophihcity of the ammo compound [5] Many polyfluonnated carbonyl compounds react likewise [22 22] On treatment of ureas [34], thioureas [34], thioamides [26], and C,77 diarylatmdmes [27, 25] first with hexa- fluoroacetone and then with dehydratmg agents, heterodienes are obtamed (equation 4)... 

The A-benzenesulfonyl imines of hexafluoroacetone readily react with nitrile oxides to give [3-1-2] adducts, apparently in a multistep reaction [151] (equation 36) Although only a few examples of [3-1-2] cycloaddition reactions of this type have been descnbed so far, most 1,3-dipoles should react in this way with predictable regiochemistry [5 146, ISO 151]... 

In accordance with FMO theory predictions,273 C2 —C4is the preferred modeofcycloaddition of tricarbonyliron and -ruthenium complexes of methyl l//-azepine-l-carboxylate with ethenetetracarbonitrile,222,274 hexafluoroacetone,222 and 2,2-bis(trifluoromethyl)ethene-l,l-dicarbonitrile 222 however, with ethenetetracarbonitrile, tricarbonyl[f/4-l-(ethoxycarbonyl)-1/f-azepine]iron(0) (1) yields a 1 6 mixture of the predicted C2 —C4 exo-adduct 2 and the C2 — C7 [6 + 2] 7i-cycloadduct 3,222 the latter heing formed by rearrangement of the former.274 Mixtures of the two adducts are also obtained with the tricarbonyliron complexes of 3-acetyl-l//-azepine and its l-(ethoxycarbonyl) derivative.274... 

Simple criss-cross cycloadditions described so far are in fact limited to aromatic aldazines and cyclic or fluorinated ketazines. Other examples are rather rare, including the products of intramolecular criss-cross cycloaddition. The criss-cross cycloadditions of hexafluoroacetone azine are probably the best studied reaction of this type. It has been observed that with azomethine imides 291 derived from hexafluoroacetone azine 290 and C(5)-C(7) cycloalkenes < 1975J(P 1)1902, 1979T389>, a rearrangement to 177-3-pyrazolines 292 competes with the criss-cross adduct 293 formation (Scheme 39). 

The reaction of hexafluoroacetone azine with cycloheptatriene at 70 °C provides after 8 days a mixture containing 28% of unchanged azine 290 and products formed by three distinct mechanistic pathways, that is, criss-cross cycloaddition product 294, a bis-ene adduct 295 and its oxidation product 296, and [3+6] cycloaddition leading to diaziridine 297, in the ratio 15 38 7 (Scheme 40) <1995JFC(73)203>. 

The reaction of quadricyclane with hexafluoroacetone azine 290 under similar conditions affords a mixture of a 1 1 adduct 298, the o , -bis-cycloadduct 299 formed by reaction of the C=N bond in 298 with quadricyclane, and the criss-cross addition product 300 (Scheme 41) <1995JFC(72)147>. 

Anderson, L. R. et al., J. Fluorine Chem., 1976, 7, 481-500 Five derivatives, including the 0-0 lithium or sodium salts of the hydrogen peroxide adduct of hexafluoroacetone (2-hydroxyhexafluoro-2-propyl hydroperoxide), and their reaction products with acyl halides, are less flammable or explosive than their hydrocarbon analogues, though less stable than the parent hydroperoxides. Relevant entries are ... 

Fig. 4.12 Enhancement of Zn(ll) extraction, D Do, from 1 M NaC104 into carbon tetrachloride containing the complexing extractants acetylacetone (O), trifluoroacetone (A), or hexafluoroacetone ( ) as a function of the concentration of the adduct former trioctyl phosphine oxide (B). The curves are fitted with Eq. (4.50) using the constants log Km = 3.01 (AA), 6.70 (TEA), 7.0 (TEA), and Km = 4.66 (AA), nil (TEA), 11.6 (HEA). (Erom Ref. 24.)...

Photochemical addition of hexafluoroacetone to (67) affords an adduct, which is formulated as the oxetane (71). 

The azomethine imine 145 from isobutylene and hexafluoroacetone azine, with DMAD, leads to a stable 1 1 adduct (146) in 90% yield.132,133... 

Hexafluoroacetone is a reactive electrophile. It reacts with activated aromatic compounds (e.g., phenol), and can be condensed with olefins, dienes, ketenes, and acetylenes. It forms adducts with many compounds containing active hydrogen (e.g., H.,0 or HCN). Reduction of HFA with NaBH or LiAlH affords the useful solvent hexafluoroisopropyl alcohol. The Industrial importance of HFA arises largely from its use 1n polymers and as an... 

A specific type of [3 -I- 2] cycloaddition reaction is the crisscross cycloadditioii between the electron-deficient hexafluoroacetone azine (6) and an electron-rich, terminal alkene or al-kyne. - Reactions can be performed under thermal or photochemical conditions and 2 1 adducts are obtained in good yields. 

U nder thermal or Lewis acid catalyzed conditions, reactions of fluoroalkyl carbonyl compounds with alkenes usually provide the ene adduct. " One example of a [2 + 2] cycloaddition between hexafluoroacetone and an alkyne has been reported. ... 

Addition of amino compounds to hexafluoroacetone occurs very readily indeed, but subsequent dehydration to form, for example, oximes or semicarbazones from the corresponding adducts does not normally occur. Special procedures usually have to be employed, the most effective being elimination of amines from adducts to form imines that are derived from the ketone, as illustrated in Figure 8.15. 

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